The air conditioner system in your car is made up of a compressor, condenser,
evaporator, expansion valve or orifice tube, receiver dry or accumulator, high
and low side hose, climate controller, fuse, relay and a switch plus some wiring
and connectors. I have made up this guide for you as I would look at a system
that was not working.
To help you know what I'm talking about throughout the
following information it would be good for you to look over
how the system works
before we begin.
Now that you have reviewed the system, there are basically two sides, the air
delivery and the refrigerant re-circulation portion of the system which includes the items
mentioned above. If the air is blowing from the vents but it's not cold this is
where we will start, if no air is coming out of the vents begin
further down in this article.
Suggested Tools and Supplies Needed
- Air Conditioner Recharge Kit
- A/C gauge set
- Leak detector
- Test light
- Basic tools
- Protective Eye wear
- Work Gloves
If any of these supplies are needed they are not to expensive and are
available at Amazon or the local parts store. Begin by parking your car on level ground with the emergency brake set, engine
cool, wearing safety eye wear and gloves.
There are two methods a compressor can control the refrigerant
flow, the first is clutch cycling, this clutch is located on the front of the
compressor and easily seen. When the system is turned on this clutch will engage
which causes the refrigerant to start flowing throughout the system.
clutch cycles on and the off within a short amount of time the system is simply
low and needs to be
The second style of compressor is designed with an internal valve which
controls the refrigerant flow, you cannot visually see if the valve working. The best
place to start in both of these situations is to plug a a/c gauge set or
recharge kit to check the level of refrigerant present in the system.
If you have attached the connector from the gauge set or recharge kit and the
system is flat with no pressure on the low side (blue) gauge there is a leak
which must be fixed. Visually inspect the system and look for oily residue which is an
indication of a leak.
If the system looks okay with the engine off use a
refrigerant leak detector and go over the hoses, condenser, compressor and
evaporator drain tube which is located on the passenger side near the floor
board on the outside of the car, when the detector starts to beep quickly the
leak has been found.
This is a list of potential failures.
- Bad compressor
- Leaking condenser
- Failed pressure hose
- Evaporator leak
- O ring seal leak
Once these items or repaired the system must be vacuumed down and recharged
to get the cold air back again.
If the charge is okay the next place I would check is the fuse which protects
the system, this fuse is located in the fuse panel or power distribution center.
By using your owners manual located the fuse and check it, if it's blown replace
it with a new one.
If in blows again once it's been replaced there is a short in the system, most of the
time this short can be related to the
compressor in which case it needs to be
When the system is switched on an electrical signal is sent to the climate
control panel and then to the a/c relay which in turn supplies power to
compressor. Locate the relay in the fuse panel or power distribution center
using the owners manual or read the bottom or top of the lid.
A relay is like an electronic switch that can handle the load of the system
where a switch would simply burn out, relay failures are common because of this
Once you have located the relay
use a test light
to check the terminals for power and
ground and then replace the relay to recheck the system.
A blend door actuator is used to control the temperature of the climate
control system by moving a door inside the heater plenum which differentiates
between hot and cold (heater core or evaporator). If the actuator is not
functioning properly usually because the plastic gears inside the unit have
stripped or are broken, it can stay either stuck in the heat or cold position or somewhere in
When it sticks in the cold position in the summer time there isn't a problem
until winter and visa versa. Sometimes when the unit fails there will be an
audible ticking noise when the ignition switch is turned on and will occur for
a short time. To test the actuator operation start you car and allow it the
engine to warm up to operating temperature, then move the temperature control
from hot to cold. You should be able to hear the door moving inside the plenum
while being able to feel the temperature change from warm to hot or hot to cool.
Also, when the blend door actuator fails you can check the low side outgoing a/c line for
coldness, this also tells you the refrigerant side of the system is working
properly. A good way to test if the system refrigerant side of the system is
working properly is to start the engine and turn the system on fully.
Next, locate the low side tube with is the larger of the two line by the
firewall and see if it's cold to the touch, you can also use an infrared hand held meter for the
If the engine is overheating the air conditioner will be weak or not working
at all. If you have been driving for sometime and you noticed the system stops
working the first thing to check it the engine temperature gauge.
It's also a good idea to use a garden hose under high pressure to flush the
a/c condenser free from built up dirt and leaves, this will help the air flow
and cool the heated refrigerant down which helps the system work better.
If when you start your car and turn the system on but there is no air coming
from the vent system you have a blower motor or blend door issue. If the blend
door has failed you will still be able to hear the fan running but not be able
to feel the air coming out of the vents. Reference the the step above for an idea
on what to expect, there are three to four actuators in every climate control
If the blower motor is not running check the fuse in the fuse panel and
replace it if necessary, if the fuse is okay then the blower motor itself might
be bad in which case the blower motor power and ground need to be tested.
If the electrical tests okay, then the blower motor itself has failed which is
common due to age and usage and needs to be replaced, these motor can be either
under the dash or hood on the passengers side.
If when the system is on and the air flow is weak but still cold, some cars are
equipped with the cabin air filter which is much like an engine air filter that
can plug causing restricted air flow. In this case the
filter must be replaced
Installing New Blower Motor
to bring back the air volume.
If you need more information about what you have just read please visit our forum
where thousands of
about air conditioners
Replacing Cabin Air Filter
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Article first published 2016-05-25